Electrical switch with the outer conductors of coaxial leads connected to spaced shield plates



April 27, 1965 s. R. M CUTCHEON ETAL 3, 8 ,086 ELECTRICAL SWITCH WITHTHE OUTER CONDUCTORS OF COAXIAL LEADS CONNECTED TO SPACED SHIELD PLATESFiled June 12, 1961 Fig. 2

26 4a 1 I I 4o 52 o i F lg. 3 2s Buckhorn, Cheafham 8 Blore ATTORNEYSUnited States Patent O" 3,181,086 ELECTREQAL SWITQH WITH THE QUEER (JQN-DUCTQRS F COAXIAL LEADS CQNNECTED TO SPACED SHEELD PLATES Samuel R.MeCutcheon, Aloha, and Chester N. Winningstad, Portland, Greg,assigziors to Telrtronix, Inc, ileaverton, Greg, a corporation of QregonFiled June 12, 1961, Ser. No. 116,358 9 Claims. (Cl. 333-7) The presentinvention relates to an electrical switch and more particularly to aswitch for changing the electrical connections between a plurality oftransmission lines having similar characteristic impedances bymechanical movement of the switch contacts.

The electrical switch of the present invention is particularly usefulfor changing the electrical connections between a plurality of coaxialcable transmission lines having substantially the same characteristicimpedance, such as those used to transmit high frequency or pulsesignals. Conventional electrical switches are not suitable in such anenvironment because they produce a discontinuity in the transmissionlines which causes undesirable reflection of signal voltages back alongthe input transmission line. In order to overcome the above problem ithas previously been suggested to provide coaxial line switches which ineffect operate by physically moving actual short sections of the coaxialcables from one position to another in order to provide continuouscoaxial lines along alternate paths without reflection of signalvoltages. However, this has not been an adequate solution to the problembecause such switches are complicated, cumbersome and expensive.

The electrical switch of the present invention overcomes thesedisadvantages byv providing broadly a simple me chanical switch in whichonly the central conductors of coaxial transmission lines are switchedin order to change connections between the transmission lines while theouter conductors of such lines are fixedly connected to commonconductors. More specifically, the switch includes a pair of spacedmetal shield plates providing common connection for the outer conductorsof the transmission lines,

and a switch plate assembly for changing the connections between theinner conductors of such lines. The switch plate assembly includes astationary stator plate and a a movable rotor plate properly positionedbetween the shield plates so that the shield plates provide in effect anequiv alent of the outer conductor of the coaxial cable transmissionlines and the switch plate assembly provides an equivalent or" thesignal carrying inner conductor of the transmission lines. This simple,inexpensive structure provides a switch in the form of a short sectionof transmission line having substantially the characteristic im pedanceof the transmission lines connected thereto.

Therefore one object of the present invention is to provide an improvedelectrical switch which permits the changing of the electricalconnections between a plurality of transmission lines without voltagereflections from said switch along said transmission lines.

Another object of the invention is to provide a simple electrical switchfor changing the electrical connections between a plurality oftransmission lines having similar characteristic impcdances so that suchswitch has a structure which is in effect a transmission line sectionhaving substantiallythe same characteristic impedance as saidtransmission lines.

A further object of the present invention is to provide a switch, tochange the electrical connections between a plurality of coaxial cabletransmission lines having similar characteristic impedances, in which aswitch plate assembly adapted to be connected to the signal carrying conductors of such lines and having a stationary stator memassists PatentedApr. 27, 1965 her and a moving rotor member is positioned in spacedrelationship between a pair of spaced electrically conducting platesadapted to be connected to the outer conductors of such transmissionlines so that the switch structure in effect forms a short section oftransmission line having substantially the same characteristic impedanceas the transmission lines connected thereto.

Additional objects and advantages of the present invention will becomeapparent upon referring to the following detailed description of apreferred embodiment of the present invention shown in the attacheddrawings of which:

FIG. 1 is a perspective View of an electrical switch made in accordancewith the present invention;

FIG. 2 is a vertical section taken along the line 2-2 of FIG. 1 showinga portion of the switch and coaxial transmission line connectionsthereto; and

FIG. 3 is a section taken along the line 3-3 of FIG. 2 showing theswitch plate and coaxial transmission lines connected thereto withconnections to the outer conductors of such lines omitted.

An electrical switch made in accordance with the present invention isshown in FIG. 1 as including a circular metal support plate it which mayhave a conventional detent switch positioning means thereon includingsuitable mechanical stops. A suitable metal or nonmetallic shaft 12 isrotatably mounted in a hole through support plate ll so that itsrotation is controlled by the detent switch positioning means on suchsupport plate 10. Two fastening bolts 14 extend through holes in thesupport plate it). A metal spacer member 16 in the form of a cylindricalsleeve is mounted on each of these bolts 14 adjacent the support plate1%). A first shieldplate 18 in the form of a circular, flat, metal platehaving a pair of holes therein to accommodate the fastening bolts 14 anda clearance hole for the shaft 12, is mounted on such bolts against thespacer 16. A switch plate assembly 20 of insulating material providedwith a pair of mounting holes for the fastening bolts 14 and a singlehole for the shaft 12, is accurately spaced from the conducting plate 13by a pair of insulating spacer sleeves 22 on the fastening bolts 1%. Asecond metal shield plate 24 having a circular shape is mounted in asimilar manner on fastening bolts 14 and spaced from switch plate 20 byinsulating spacer sleeves 26 similar to sleeves 22. Circular shieldplates 18 and may have the same diameter and are provided with aconcentric clearance hole through which the shaft 12 extends so that itis free to rotate without contacting the surface of such conductiveplates. The switch assembly may be held on fastening bolts 14 andsupport plate lii by means of a nut and lock washer combination 3th onthe threaded end or" such fastening bolts 14.

FIG. 2 shows coaxial cable transmission lines 32 connected toappropriate switch members including a pair of electrical connectors 34extending between the grounded outer conductor 35 of each coaxial cable32 and the common shield plates 18 and 24. Switch plate assembly 29includes two concentric circular insulating members 36 and 38. The outerinsulating member is a fixed annular stator plate 36 positioned on thefastening bolts 14 between insulating spacer members 22 and 26, whilethe inner insulating member is a circular rotor plate 38 having a holetherein fitting a flattened portion of the shaft 12 so as to be rotatedby the shaft. The stator plate 36 has a plurality of pairs of fixedmetal spring contacts 40 attached in spaced relationship around thestator plate so as to extend radially thereof. These fixed contacts 40are each in the form of a spring member having an end which extendsoutwardly from the outer periphery of the stator plate 36 for connectionto the central conductor 44 of a coaxial cable, such as the cables 32,by soldering or the like. The rotor plate 38 is provided with aplurality of metal contact plates 46 in spaced insulated relationshipwhich extend along the periphery of the rotor plate 38 and for a shortdistance over the inside edge of the stator plate 36 so that the outersurface of the contact.

plates 4-6 make mechanical contact with the spring ends of the fixedcontacts 40 upon rotation of the shaft 12.

.It should be noted that the switch plate assembly 20 is symmetrical inthat a pair of fixed contacts 46 and a pair of movable contact plates 46are attached by rivets 48 to such assembly with one element of the pairon each side of the stator plate 36 and rotor plate 33, respectively.One reason for this symmetrical arrangement is to minimize theelectrical field which passes through the insulat ing stator plate 36and insulating rotor plate 33 when signal voltages are transmittedthrough the switch so that dielectric losses therein are minimized. Eachof the parallel shield plates 18 and 24 is placed substantially the samedistance from the switch plate assembly 20 so that the switch is alsosymmetrical in this respect. The distances between the shield plates 18and 24 and contacts 40 and 4c are such that the switch forms in effect ashort section of a transmission line having a characteristic impedancesubstantially the same as that of the coaxial cable transmission lines32. For example, when the coaxial cables 32. have a characteristicimpedance of 50 ohms and the contacts 40 and 46 have a width ofapproximately A; inch, the space between such contacts and theconductive plates 18 and 24 should be approximately one-tenth of aninch. As a result, voltage reflections in the transmission lines 32 dueto the line discontinuity formed by a switch are substantiallyeliminated by the switch of the present invention.

In FIG. 3 the coaxial cables 32 are shown as being connected to thecenter contact of two oppositely disposed groups of three contacts 40 onthe stator plate 36. The rotor plate 38 may be rotated by the shaft 12between two alternate positions in order to change the connectionsbetween the coaxial cables shown. In the position of the switch shown inFIG. 3 the input signal can enter the switch through one of thetransmission lines 3-2, then pass through the connection formed by fixedcontacts 40 and the movable contact plates 46 and by the connectingtransmission line 2 to the other transmission line 32 which may be theoutput transmission line. Moving the rotor plate 38 counterclockwise toits alternate position will cause the signal to move through theconnecting transmission line 54 so that it may be attenuatedby anattenuator 56, or otherwise modified by any other suitable modifyingmeans, before it is transmitted to the output transmission line. Agreater number of switch contacts can be employed on the switch plateassembly for any switching purpose involving coaxial cable transmissionlines or the like, usually with some loss of symmetry of the switch andsome lack of continuity of the transmission line.

It should be understood that many variations in the detailsofthe presentinvention may be made without departing from the spirit of the presentinvention.

other than circular, and the type of connectors 40 and 46 can be variedwithout departing from the scope of the present invention. Therefore, itis not intended to limit the present invention to the preferredembodiment de-' scribed above but the scope of the invention should bedetermined solely by the following claims. i

. We claim:

1. A switch to change the electrical connectionsbe For example, theshapeof the plates 10, 18, 20 and 24 may be.

switch means including switch contacts positioned betweenthe shieldplates for interconnecting the other conductors of said transmissionlines in a plurality d of ditferent ways by movement of said switchmeans, and g I support means to hold said shield plates and said switchcontacts in proper spaced relationship to form a trans mission linesection having substantially the same characteristic impedance as saidtransmission lines. I

2. A switch to change the electrical connections between a plurlity oftransmission lines each having a pair of conductors and having similarcharacteristic impedances, comprising:

shield means including a pair of spaced shield plates to provide acommon connection for the ends of one of for interconnecting said fixedcontacts in a plurality of ditferent ways by movement of said switchmeans, and 7 support means to hold said shield plates, said fixedcontacts and said movable contact in proper symmetrical spacedrelationship to form a transmission line section having substantiallythe same characteristic impedance as said transmission-lines.

3. A switch, used to change the electrical connections between'aplurality of coaxial cable transmission lines having inner and outerconductors and having similar characteristic impedances, comprising:

shield means including a pair of spaced shield plates to provide acommon connection for ends of the outer conductors in said transmissionlines,

switch means including a plurality of fixed switch contacts positionedbetween said shield plates to provide a plurality of spaced insulatedconnectors adapted to be connected to ends of the inner conductors insaid transmission lines,

switch means also including at least one movable switch contactpositioned between said shield plates for interconnecting said fixedcontacts in a plurality of ways by movement of said movable contact, andsupport means to hold said movable and fixed contacts approximatelymidway between said shield plates to form a transmission line sectionhaving substantially the same characteristic impedance as said co- 7axial cable transmission lines;

4. A switch, used to change the electrical connections between aplurality of transmission lines having similar characteristicimpedances, comprising:

a pair of spaced shield plates of electrically conductive 7 materialadapted to provide common connections for the ends of shield conductorsin said transmission 7 lines, 1 A a fixed switch plate having aplurality of insulated fixed switch contacts positioned between saidpair ,of shield plates and adapted to be connected to the ends of signalconductors in said transmission lines, .a'rotatable switch plate havingat least one movable contact positioned between said shield plates forinterconnecting said fixed contacts in a plurality of ways by rotationof said rotatable switch plate, and support means to hold said fixed andmovable switch plates approximately midway between said shield plates toform a transmission line section having substantially the samecharacteristic impedance as 7 said transmission lines. 5. A-switch forchanging the electrical connections betweena plurality of electricaltransmission lines having adapted to be connected to the shieldconductor in said transmission lines,

a stator plate of insulator material mounted between said shield platesand having a hole therein,

d on said shaft for rotation therewith inside said hole in said statorplate, a plurality of movable metal contacts attached to said rotorplate in spaced relationship adjacent the pea rotor plate of insulatormaterial mounted between 5 riphery thereof for movement with said rotorplate. said shield plates and inside said hole for rotation a pluralityof fixed metal connectors attached to said with respect to said statorplate, stator plate in spaced relationship and extending raa pluralityof movable metal contacts attached to the dially from said hole in saidstator plate so that one surface of said rotor plate in spaced,insulated relaend of said connectors is positioned adjacent thepetionship adjacent the periphery thereof for movement riphery of saidhole and is adapted to engage said with said rotor plate, contacts onsaid rotor, and the other end of said conand a plurality of fixed metalcontacts attached to the nectors is positioned adjacent the outside edgeof said surface of said stator plate in spaced relationship and statorplate and is adapted to be connected to the extending radially from saidhole so that one end of signal carrying inner conductor of saidtransmission each of said fixed contacts is positioned to engage lines,said movable contacts on said rotor plate, and the said plurality ofcontacts and said plurality of connecother end of said fixed contacts isadapted to be contors being accurately positioned between said pair ofnected to the signal carrying conductors in said transshield plates inorder to form a transmission line secmisslon lines, tion whosecharacteristic impedance is substantially and means to support saidshield plates in proper spaced the same as the characteristic impedanceof said relationship with respect to said stator plate and said rotorplate to form a transmission line section having transmission lines. 8.A coaxial line switch to change the electrical connecsubstantially thesame characteristic impedance as tions between a plurality of coaxialcable transmission said transmission lines. lines each havingsubstantially the same characteristic im- 6. A switch for changing theelectrical connections bepedance, comprising: tween a plurality ofelectrcal transmission lines having a support member having a detentswitch positioning substantally the same characteristic impedancecomprismeans thereon,

a pair of spaced shield plates of conductive material ing: a shaftrotatably mounted on said support member,

a plurality of fastening elements fixedly mounted on adapted to beconnected to the shield conductors in said support member, saidtransmission lines, a pair of substantially parallel spaced shieldplates of a stator plate of insulator material positioned betweenelectrically conductive material fixedly mounted on said shieldplatesand having a hole therein, said fastening elements in spacedrelationship and a rotor plate of insulator material mounted between 7adapted to be connected to the outer conductor of said shield plates andinside said hole for rotation said coaxial cables with the shield platenearest said with respect to said stator plate, support member having ahole through which said a plurality of movable metal contacts attachedin pairs shaft extends while spaced from said nearest shield to theopposite sides of said rotor plate with respect plate, to said shieldplates in spaced, insulated relationship a stator plate of insulatormaterial having a substantially adjacent the periphery thereof formovement with circular hole therein fixedly mounted on said fastensaidrotor plate, ing elements and spaced between said pair of shield and aplurality of fixed metal contacts attached in pairs plates, said statorplate having two opposite side to the opposite sides of said statorplate with respect surfaces, to said shield plates in spacedrelationship and exa substantially circular rotor plate of insulatormaterial tending radially from said hole in said stator so thatcoaxially mounted on said shaft for rotation there one end of each ofsaid connectors is positioned adwith inside said hole in said statorplate, said rotor jacent the periphery of said hole adapted to engageplate having two opposite side surfaces, said contacts on said rotorplate, and the other end a plurality of movable metal contacts attachedin pairs of said connectors is positioned adjacent the outside to theopposite sides of said rotor plate with respect edge of said statorplate adapted to be connected to to said shield plates in spacedrelationship adjacent the signal carrying conductors in saidtransmission the periphery thereof for movement with said rotor lines,and plate, means to support said stator plate and said rotor plate aplurality of fixed metal contacts attached in pairs to approximatelymidway between said shield plates the opposite sides of said statorplate with respect to to form a transmission line section havingsubstansaid shield plates in spaced relationship and extending tiallythe same characteristic impedance as said transmission lines. 7. Acoaxial line switch, used to change the electrical radially from saidhole in said stator plate so that one end of said fixed contacts ispositioned adjacent the periphery of said hole and is adapted to engagesaid connections between a plurality of transmission lines each havingsubstantially the same characteristic impedance, a0 comprising:

movable contacts on said rotor, and the other end of each of said fixedcontacts is positioned adjacent the outside edge of said stator plateand is adapted a support member, a shaft rotatably mounted on saidsupport member, a plurality of fastening elements fixedly mounted on tobe connected to the signal carrying inner conductor of said coaxialcables, and a plurality of insulating spacers accurately positioningsaid support member, 5 said plurality of pairs of movable contacts andsaid a pair of spaced shield plates of electrically conductive pluralityof pairs of fixed contacts approximately material fixedly mounted onsaid fastening elements midway between said pair of shield plates inorder to in spaced relationship and adapted to be connected to form atransmission line section whose characteristic the grounded outerconductor of said transmission impedance is substantially the same asthe character lines with the shield plate'nearest said support mem- 7istic impedance of said coaxial cables. her having a hole through whichsaid shaft extends, 9. A transmission line switch assembly comprising:

a stator plate of insulator material having a hole therea plurality oftransmission lines each having a pair of in fixedly mounted on saidfastening elements and conductors and having similar characteristicimpedspaced between said pair of shield plates, ances,

a rotor plate of insulator material coaxially mounted shield meansincluding a pair of spaced shield plates '2! 8 connected to one of theconductors to provide a comsame characteristic impedance as saidtransmission mon connection for one of the conductors of each of lines.said transmission lines, References Cited by the Examiner switch meansincluding switch contacts positioned be- V UNITED STATES PA tween theshield plates for inter-connecting the other 5 1 891 47 12/ 2 h Aconductors of said transmissionlines in a plurality of 5 1 g zf g 3555Ways by movement of, sad W11 214401037 4/48 Wolfi 200-11 2,598,534 5/52Gordon 20() 11 support means to hold said shield plate and said switch2,784,379 3/57 Schunemann 333 7 contacts in proper spaced relationshipto form a 1Q transmission line section having substantially the HERMANKARL SAALBACH, Primary Examiner.

1. A SWITCH TO CHANGE THE ELECTRICAL CONNECTIONS BETWEEN A PLURALITY OFTRANSMISSION LINES HAVING A PAIR OF CONDUCTORS AND HAVING SIMILARCHARACTERISTIC IMPEDANCES, COMPRISING: SHIELD MEANS INCLUDING A PAIR OFSPACED SHIELD PLATES TO PROVIDE A COMMON CONNECTION FOR ONE OF THECONDUCTORS OF EACH OF SAID TRANSMISSION LINES,